Multiple zone production drive process



PRODUCTION AIR June 6, 1967 PRODUCTION HOT FLUID III III

R. E. GILCHRIST ETAL MULTIPLE ZONE PRODUCTION DRIVE PROCESS Filed Oct. 28, 1964 INVENTORS RE. GILCHRIST W.B. LUMIPKIN J. c. TRANTHAM A TTO/PNEIS United States Patent 3,323,590 MULTIPLE ZONE PRODUCTION DRIVE PROCESS Ralph E. Gilchrist, William B. Lumpkin, and Joseph C.

Trantham, Bartlesville, Okla., assignors to Phillips Petroleum Company, a corporation of Delaware Filed Oct. 28, 1964, Ser. No. 407,144 12 Claims. (Cl. 166-11) This invention relates to a process for producing oil from a plurality of adjacent subterranean strata by a hot drive. i

The production of highly viscous crude oil by conventional methods is quite diflicult and presents special problems. Various methods have been proposed to reduce the viscosity of the crude, especially by heating the formation or stratum containing the same with hot gases, steam, or fire flood (in situ combustion). Thise methods are relatively wasteful because the heat generated in a producing zone is largely wasted by conduction into non-productive zones and the hot produced oil-containing eflluent merely serves to heat the producing string which is undesirable.

In various oil fields several producing zones of varying permeability and containing crude oil of varying viscosities exist at different levels. This invention is concerned with a process for producing crude oil from such zones or strata with more eificient utilization of heat generated.

Accordingly, it is an object of the invention to provide a process for producing crude oil from a premeable oilbearing stratum lying close to at least one other permeable stratum which may or may not contain oil. A further object is to provide a process for producing a permeable stratum bearing crude oil by in situ combustion with more eflicient utilization of heat from the producing stratum. Another object is to provide improved utilization of heat in multiple zone production of oil. Other objects of the invention will become apparent upon consideration of the accompanying disclosure.

A broad aspect of the invention comprises producing oil from a permeable stratum bearing crude oil is situ combustion and simultaneously passing a hot fluid, such as steam, thru an adjacent permeable stratum, heat exchanging the stream with the hot effluent from the in situ combustion operation by indirect heat exchange in the production well and also effecting indirect heat exchange between the effluent from the steam operation and the injected air in the air injection well for the in situ combustion operation. In this manner the steam absorbs heat from the produced in situ combustion eflluent and the injected air absorbs heat from the steam injection operation. It is to be understood that other hot fluids such as hot water, hot gases other than steam (combustion gases), normally gaseous hydrocarbons, etc, may be used in the process. The premeable stratum thru which the hot fluid is passed from the production well to the injection well preferably contains oil so that oil is produced from this stratum along with the stratum undergoing in situ combustion.

TlTe in situ combustion operation may comprise a forward or reverse drive process. In a forward drive process the oil is ignited around the injection well, driving the resulting combustion zone toward an oflset production well. In a reverse drive operation, the ignition is eflected around a production well and air or other O -containing, combustion-supporting gas is injected thru an oflset injection well, traveling thru the stratum to the combustion zone around the production well and moving the combustion zone toward the injection well. In either type of process there is substantial heating of the strata above and below the producing zone and this heat can be utilized in producing other strata above and/ or below the producing zone.

A more complete understanding of the invention may be had by reference to the accompanying schematic drawing which is an elevation thru a section of an oil field penetrated by a pair of wells.

Referring to the drawing, satrum 10* is a permeable oilbearing stratum lying adjacent stratum 12 which also is a permeable oil-bearing startum. These strata may or may not be separated by an impervious shale or other layer 14. Numeral 1'6 designates a third premeable stratum overlying stratum 10 and it may be separated therefrom by an impermeable layer 18. Straturm 16 may or may not contain oil. The various strata are penetrated by Wells 20 and 22 which are provided with casing strings 24 and 26, respectively. A tubing string 28 extends from above the well head to stratum 10 and a second tubing string 30 concentric with string 28 extends into stratum 12 and is packed off at the level of layer 14 by a suitable packer 32. Production line 34 connects with tubing 28 and an air line 36 connects with tubing 30. Casing string 24 is shown extending to the upper level of stratum 16, however, this casing may extend thru the several strata and be perforated within the strata for production in known manner. This is also true of casing 26.

In well 22 a similar arrangement of tubing strings 33 and '40 is provided, the packer 42 packing oil the lower end of the Well within stratum 12 so that tubing string 40 is open to this stratum.

In the operation illustrated in the drawing, in situ combustion zone 44 has been moved into stratum 12 by igniting the oil in this stratum around well 22 and injecting combustion-supporting gas (air) thru tubing 30 in Well 20 so that the injected gas passes thru stratum 12 to the combustion zone and propagates same toward well 20 in a reverse drive operation. The produced fluids pass thru tubing string 40 to production line 46.

After the combustion zone has been established in stratum 12 and driven a short distance, stream or other hot fluid is injected thru line 48 and tubing 38 so that the hot fluid absorbs heat from the production eflluent from stratum 12. Normally the temperature of the production eflluent is above 800 and usually above 1000 P. so that steam injected at 300400 F. thru tubing 38 absorbs a substantial amount of heat from the production eflluent and substantially reduces the temperature thereof. The production effluent must be cooled above ground to condense hydrocarbons and water therefrom. This indirect heat exchange step therefor effects needed cooling and also carries the heat absorbed into stratum 10 which it is assumed is an oil-bearing stratum for purposes of illustration. Hence the hot steam effects a hot drive of oil thru stratum 10 into well 20 above packer 32 from which production is recovered thru tubing 28. This hot effluent is indirectly heat exchanged with the injected air so as to reduce the heat requirements in stratum 12 for maintaining and propagating the in situ combustion front.

During the foregoing operations, heat from stratum 12 passes into stratum 10 to assist in the production of oil therein which is rendered substantially less viscous than originally by the heating eflect. In this operation, the temperature in stratum 10 is several hundred degrees below the combustion temperature in stratum 12.

For purposes of illustration, stratum 16 contains a highly viscous crude which is rendered substantially less viscous by the heat transferring from stratum 10 during the production of strata 10* and 12. This less viscous oil in stratum 16 is substantially less diflicult to produce than prior to the heating thereof. Production of stratum 16 to recover the less viscous oil is then effected thru wells 24 and 26 by rearranging the tubing strings to provide separate flow paths to this stratum thru each well. In the event stratum 16 is a permeable stratum containing oil and is to be produced, packers 50' and 52 are set before production of strata and 12. This prevents flow of fluid from either well into stratum 16 until after the heating of this stratum has been effected. The production of stratum 16 after the heating thereof is continued by fluid drive or in situ combustion, depending upon the permeability of the stratum to air after the heating operation.

To illustrate another type of operation involving multiple permeable zones it is assumed that stratum 10 contains a highly viscous crude oil and is of relatively low permeability While strata 12 and 16 contain less viscous crude oil and are substantially more permeable. Strata 12 and 16 are produced simultaneously by in situ combustion and hot fluid drive as heretofore described with reference to strata 10 and 12. The heat from the in situ combustion in one stratum and hot fluid drive in the other results in substantial heating of stratum 10 from both the upper and lower zones which substantially reduces the viscosity of the oil therein and render this stratum more amenable to production. The conduit system is readily rearranged for this type of operation as will be understood by one skilled in the art.

Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

We claim:

1. A process for simultaneously producing oil from first and second oil-bearing permeable strata penetrated by a pair of spaced wells which comprises the steps of:

(a) igniting oil in said first stratum adjacent one of said wells;

(b) feeding a stream of O -containing, combustionsupporting gas to the combustion zone resulting from step (a) thru one of said wells so as to move said zone thru said first stratum toward the other of said wells;

(c) recovering produced hot eflluent from step (b) thru one of said wells;

(d) simultaneously injecting hot fluid at a temperature below that of the hot effluent of step (c) thru said one of said wells of step (c) thru a separate flow path in indirect heat exchange with said hot effluent;

(e) passing the hot fluid of step (d) thru said second stratum to the other of said wells to effect a hot fluid drive therethru to produce oil therefrom;

(f) passing the hot effluent from step (e) thru a separate flow path thru said other well in indirect heat exchange with the combustion-supporting gas of step (b); and

(g) recovering the cooled effiuent from step (f).

2. The process of claim 1 wherein the hot fluid of step (d) comprises steam.

3. The process of claim 1 wherein the hot fluid of step (d) comprises hot liquid.

4. The process of claim 1 wherein the hot fluid of step (d) comprises hot gas.

5. A process for simultaneously producing oil from closely spaced first and second oil-bearing permeable strata penetrated by first and second spaced wells, which comprises the steps of:

(a) moving a reverse burning combustion zone thru said first stratum from said first well toward said second well by igniting the oil in said first stratum adjacent said first well and injecting air thru said second well and recovering produced hot effluent containing oil thru said first well;

(b) simultaneously injecting a hot driving fluid at a temperature below that of the produced hot efliuent of step (a) thru said first well via a separate flow path in indirect heat exchange with said hot efiiuent into said second stratum so as to drive oil therefrom into said second Well; and

(c) recovering the produced hot effluent of step (b) from said second well thru a separate flow path in indirect heat exchange with the injected air of step (a).

6. The process of claim 5 wherein the hot fluid of step (b) is steam.

7. The process of claim 5 wherein the hot fluid of step (b) is hot liquid.

8. The process of claim 5 wherein the hot fluid of step (b) is hot gas.

9. The process of claim 5 wherein said first and second strata are sufliciently closely spaced that heat from the in situ combustion in the first stratum substantially heats said second stratum and the combustion zone is moved a substantial distance into said first stratum in step (a) before initiation of fluid drive in step (b).

10. The process of claim 5 wherein said first and second strata are separated by a third less permeable stratum containing viscous crude and heat from said first and second strata invades said third stratum and renders the oil therein substantially less viscous; and including the step of producing said less viscous oil.

11. A process for producing oil from a permeable oilbearing stratum lying adjacent a second permeable stratum, the two strata being penetrated by a pair of wells, which comprises the steps of:

(a) conducting an in situ combustion drive between said wells by igniting the oil-bearing stratum adjacent one of said wells, feeding a stream of combustion-supporting, O -containing gas to the combustion zone thru one of said wells, and producing hot effluent containing oil thru the other well;

(b) simultaneously passing a hot fluid at a temperature substantially below the temperature of the eflluent in step (a) thru said other well in indirect heat exchange with said efliuent so as to cool said eflluent and heat said hot fluid;

(c) passing the heated fluid of step (b) thru said second permeable stratum so as to heat same substantially, reduce heat loss from said oil-bearing stratum adjacent said combustion, and heat same in advance of said combustion zone; and

(d) passing the efi luent from step (c) thru said one Well in indirect heat exchange with said combustion-supporting gas so as to preheat same and cool last sa'd efliuent.

12. The process of claim 11 wherein the combustion zone in step (a) is moved by reverse drive.

References Cited UNITED STATES PATENTS 2,217,749 10/1940 Hewitt 166--10 3,050,116 8/1962 Crawford l6611 X 3,054,448 9/1962 Dew et al. 1661l 3,163,215 12/1964 Stratton 16611 X 3,180,413 4/1965 Willrnan 16611 CHARLES E. OCONNELL, Primary Examiner.

JACOB L. NACKENOFF, Examiner.

S. J. NOVOSAD, Assistant Examiner, 

11. A PROCESS FOR PRODUCING OIL FROM A PERMEABLE OILBEARING STRATUM LYING ADJACENT A SECOND PERMEABLE STRATUM, THE TWO STRATA BEING PENETRATED BY A PAIR OF WELLS, WHICH COMPRISES THE STEPS OF: (A) CONDUCTING AN IN SITU COMBUSTION DRIVE BETWEEN SAID WELLS BY IGNITING THE OIL-BEARING STRATUM ADJACENT ONE OF SAID WELLS, FEEDING A STREAM OF COMBUSTION-SUPPORTING, O2-CONTAINING GAS TO THE COMBUSTION ZONE THRU ONE OF SAID WELLS, AND PRODUCING HOT EFFLUENT CONTAINING OIL THRU THE OTHER WELL; (B) SIMULTANEOUSLY PASSING A HOT FLUID AT A TEMPERATURE SUBSTANTIALLY BELOW THE TEMPERATURE OF THE EFFUENT IN STEP (A) THRU SAID OTHER WELL N INDIRECT HEAT EXCHANGE WITH SAID EFFLUENT SO AS TO COOL SAID EFFLUENT AND HEAT SAID HOT FLUID; (C) PASSING THE HEATED FLUID OF STEP (B) THRU SAID SECOND PREMEABLE STRATUM SO AS TO HEAT SAME SUBSTANTIALLY, REDUCE HEAT LOSS FROM SAID OIL-BEARING STRATUM ADJACENT SAID COMBUSTION, AND HEAT SAME IN ADVANCE OF SAID COMBUSTION ZONE; AND (D) PASSING THE EFFLUENT FROM STEP (C) THRU SAID ONE WELL IN INDIRECT NEXT EXCHANGE WITH SAID COMBUSTION-SUPPORTING GAS SO AS TO PREHEAT SAME AND COOL LAST SAID EFFLUENT. 